1. Field of the Invention
The present invention relates to a winding structure for a rectangular wire.
Priority is claimed on Japanese Patent Application No. 2011-239121, filed Oct. 31, 2011, the contents of which are incorporated herein by reference.
2. Description of Related Art
Generally, in an electric motor (i.e., a brushless motor) that is composed of a rotor in which magnets are provided, and of a stator core around which wire is wound, the performance of the electric motor improves proportionally as the density of the winding wires that is wound around the teeth portion of this stator core (i.e., the space factor) increases. For this reason, a structure is known in which, in order to make it easier to wind the winding wires around the teeth portion, laminated core piece segments that each include a teeth portion are provided separated from each other in the circumferential direction and extending in the axial direction of the electric motor. By providing this type of structure, winding wires can be firstly wound around each of the segmented laminated core pieces, and the segmented laminated core pieces can then be assembled together to form the stator core. As a result, the space factor can be improved.
Both winding wires that are formed by what are known as round wires, which have a circular cross-section, and winding wires that are formed by what are known as rectangular wires, which have a substantially rectangular cross-section, are known. Because of the characteristics provided by the shape of rectangular wires, the gaps between winding wires within the stator core are smaller compared to round wires. As a result, the space factor can be improved even further.
The technology disclosed in Japanese Patent Application, First publication No. 2008-61442 is known as a technology that improves the space factor when rectangular wires are wound around the teeth of the laminated core pieces. In the technology disclosed in Japanese Patent Application, First publication No. 2008-61442, the winding wires are wound around the teeth such that, round wire is being molded into rectangular wire, the cross-sectional shape of the rectangular wire changes in each lamination (i.e., winding layer) of the rectangular wire, the gap between the rectangular wire and the teeth is the minimum size, thereby improving the space factor.
Generally, the electric wire that is used for the winding wires of an electric motor is formed by covering the surface of a copper wire material with an enamel coating. If the cross-sectional configuration of a round wire that has an enamel coating provided on its surface in this manner is changed by being molded into a rectangular wire, the enamel coating comes under stress when the round wire is being molded into a rectangular shape. Because of this, there is a deterioration in flexibility when the wire is subsequently wound around the teeth. Here, the term ‘flexibility’ refers to the ability of the enamel coating to follow the rectangular wire being bent. If the flexibility of the enamel coating deteriorates, then it is unable to follow the bending of the rectangular wire, and in some cases the enamel coating may become damaged.
Accordingly, in order to improve the space factor, it is not feasible to change the cross-sectional configuration when a round wire is being molded into a rectangular wire.
It is an object of the foregoing invention to provide a winding structure for a rectangular wire that makes it possible to improve the space factor of a rectangular wire while limiting any reduction in the flexibility of the rectangular wire.